Twitter told congressional investigators Thursday that it pulled down 201 accounts linked to Russian entities that purchased ads on Facebook.

The revelation comes as other tech firms, including Facebook and Google, are under growing political pressure to look more closely at how their sites were used to try to influence the U.S. presidential election.

“Twitter deeply respects the integrity of the election process, which is a cornerstone for all democracies,” the company said in a blog post.

Separately, Twitter also revealed that the news site RT (Russia Today), which the company noted has links to the Russian government, spent $274,100 for U.S. ads in 2016. The news agency used three accounts to promote 1,823 tweets.

Russian government officials have denied they used social media sites to meddle in the U.S. election, and President Donald Trump has dismissed the allegations as part of a “hoax.”

But Facebook recently found 470 accounts and more than 3,000 ads that likely have ties to Russia. The company is turning over these ads to congressional investigators.

Twitter looked into the Russian-linked accounts on Facebook and found 22 corresponding accounts on Twitter. The tech firm then discovered another 179 related or linked accounts. Most of the accounts were pulled down because of Twitter’s rules against spam.

“Neither the original accounts shared by Facebook, nor the additional related accounts we identified, were registered as advertisers on Twitter,” the company said.

Twitter Vice President for Public Policy Colin Crowell met with staff from the Senate’s and House’s intelligence committees on Thursday to discuss the company’s findings.

Twitter, which has 328 million users, outlined some of the tools it uses to identify suspicious bots and content on the site.

With more than 2 billion users worldwide, Facebook’s audience is much larger than Twitter’s. But Twitter is popular with President Trump and, unlike Facebook, doesn’t require users to provide their real names.

Some U.S. lawmakers, including Sen. Mark Warner, were not pleased with the company’s testimony.

Warner, D-Virginia, has been working on legislation that would require social media companies to keep a public file of election ads and communications. The firms would also need to make a “reasonable” effort to ensure that election ads are not purchased indirectly or directly by a foreign national, according to a letter by Warner and Sen. Amy Klobuchar, D-Minnesota.

Warner told reporters that he thought Twitter’s response was “inadequate,” noting that the company’s findings came from accounts Facebook identified.

He then followed up his remarks with a post on Twitter.

“Frankly I don’t think they understand how serious this problem is,” Warner tweeted.

Damian Collins, a member of Parliament who chairs the Digital, Culture, Media and Sport Select Committee, attacked the social media giant for failing to address his questions about possible Russian interference in the 2016 referendum to leave the European Union and the June election.